1. Field of the Invention
The present invention relates to a punching device which punches a hole of a specified shape in a plate shaped workpiece, and to a workpiece processing method which utilizes this punching device.
2. Description of the Prior Art
When punching a hole of a specified shape in a plate shaped workpiece, a punching device has been employed which comprises a die in the upper surface of which a die hole is formed, and a punch which can be raised and lowered with respect to this die so as to enter into the die hole of the die. And a pattern which shows the positions to be punched is provided upon a workpiece which can be processed by being punched using this type of punching device, so that the punching process can be performed with high accuracy when this pattern is accurately aligned with the die hole. In order to do this, a punching device has been developed in which a photographic device is provided for detecting the position of the workpiece. In this punching device, position determination for the punching process is performed by shifting the workpiece to a position in which it can be photographed by the photographic device, and when performing punching, the workpiece is further shifted to the correct position for being punched.
Furthermore, a punching device in which the position of the workpiece is detected by photography without shifting the workpiece has been developed, and has been disclosed in Japanese Patent Application, First Publication No. Hei 10-118995. This punching device performs position determination of the workpiece by shifting the photographic device to an axis which joins the die hole of the die and the punch, and when punching is to be performed, the photographic device is removed away from the above described axis, so that the punching process can be performed.
However, with the former prior art punching device, when shifting the workpiece from the photographic position to the punching position, there is the problem that the accuracy deteriorates due to occurrence of positional deviation between the workpiece and the die, and also that the accuracy becomes further deteriorated due to the length of the distance through which shifting is performed. In addition, the problem also arises that the work efficiency is poor, because, after the shifting has stopped, it is necessary to wait until vibration set up by the shifting has died away.
Furthermore, with the latter prior art punching device, the problem arises that detection of the position of the workpiece at high accuracy cannot be anticipated, since the photographic device is frequently shifted, and accordingly the position of the photographic device when detecting the position of the workpiece is not necessarily always the same.